Manufactures even today use paint break stripes. Why because they are easy !! A good example is the 1971-73 Mach 1 Mustang. The lower section of the car was painted at the factory but the paint did not have a finished edge. So they feathered the paint at the edge and install a paint break stripe #835 to finish the edge. So it is just as it sounds it is decal over the painted section.
Other Products using Paint Break Method:
A651 - 1977-79 Ford Ranchero GT - Lower Paint Break Stripe Kit
M401 - 1973 Ford Maverick Side and Trunk Stripe Kit - Paint Break side stripes
QG-397 - 1971-72 Plymouth Duster Twister Ladder Hood Treatment
QG-536 - 1971-72 Dodge Demon Snorkel Scoops Hood Paint Break Stripe Kit
QG-832 - 1991-93 Dodge Dakota Truck Mid Body Paint Break Stripe